let ban=document.querySelector(".banner_child");
let a=0;
let imgs=document.querySelectorAll(".banner_child img");
let lis=document.querySelectorAll(".banner_child li");
timer=setInterval(()=>{
    a++;
    a==imgs.length&&(a=0);
    act(a);
},3000);
console.log(ban);
ban.onclick=e=>{
    let tg=e.srcElement;
    if(tg.nodeName=="LI"){
        let b=tg.getAttribute("qwe");
        act(b);
    }
}
ban.onmouseover=()=>{
    clearInterval(timer);
}
ban.onmouseout=()=>{
    timer=setInterval(()=>{
        a++;
        a==imgs.length&&(a=0);
        act(a);
    },3000);
}
function act(th){
    imgs.forEach((val,i)=>{
        imgs[i].className="";
        lis[i].className="";
    });
    imgs[th].className="light";
    lis[th].className="lit";
}
    